1. Technical Field
The present invention relates to a primary transfer device and an image forming apparatus provided with the same.
2. Related Art
Usually, as a color image forming apparatus such as a color copying machine or a color printer to which an electro-photographic system is applied, an image forming apparatus of what is called an intermediate transfer system has been known that includes a plurality of image forming units corresponding to colors such as yellow (Y), magenta (M), cyan (C) and black (K). In this image forming apparatus, toner images of the respective colors sequentially formed on photosensitive drums of the image forming units are temporarily primarily transferred in multiple forms to an intermediate transfer member by primary transfer devices respectively opposed to the photosensitive drum. Then, the toner images of the respective colors multiply transferred to the intermediate transfer member are secondarily transferred together to a recording medium by a secondary transfer device. After that, the toner images are heated, pressed and fixed to the recording medium to form a color image. In the primary transfer device in the image forming apparatus using such an intermediate transfer member, primary transfer rolls are respectively arranged so as to be opposed to the photosensitive drums through, for instance, an intermediate transfer belt as an endless type intermediate transfer member to form a primary transfer part, and a pressure contact force and an electrostatic force are allowed to act on the primary transfer part to transfer the toner images formed on the photosensitive drums to the intermediate transfer.